In recent years, many power converters that perform power conversion from direct current to alternate current are used. Such power converters are widely applied to the field of high voltage, and there are for example power converters configured by serially connecting plural switching elements including a semiconductor controllable switch.
A power converter applied in the field of high voltage is configured, for example, by arranging valve branches each of which is formed by serially connecting switching elements, and further arranging legs by serially connecting these valve branches in a plural number. In the power converter, connection points of valve branches of the legs are connected to the respective phases of AC terminals, and the both ends of these legs are connected to DC terminals. The power converter controls currents flowing in the respective valve branches by controlling the operation of the respective switching elements, and power conversion between AC terminals and DC terminals can be thus performed.
In respective switching elements that construct a voltage source converter, the fewer the electrical wires are, the more suitable it is for reducing negative effects of serge by a high voltage and the like, and a configuration with which the switching elements independently operate by an internal power source (self-supply power source) is desirable. There are switching elements each of which includes a semiconductor controllable switch, a capacitor, a driver circuit of the semiconductor controllable switch, a control circuit, and further an internal power source circuit for supplying power to the switching element itself.
As an object of Patent Document 1, described is ‘In case of controlling a power converter configured by connecting cells, each of which use a semiconductor controllable switch, in a form of plural cascades, it is necessary to perform communication between a plurality of cells and a central control device, wherein the information amount of communication and the load of information processing increase by an increase in the number of cells. An object of the present invention is to reduce information amount in communicating between respective cells and a central control device.’ As means for solving the problem, described is ‘According to the present invention, a power converter includes a plurality of valve branches formed by connecting a plurality of cells in a cascade form, and is provided with a function to supply power from a main circuit to the cell control devices, of the respective cells, performing communication with a central control device.’ As an advantage, described is ‘In the power converter according to the invention, by supplying power from a main circuit to the cell control devices of respective cells, when main components of cells are in failure and communication with the cell control devices of these cells becomes disabled, the central control device can recognize that these cells are in failure.’